Liquid fuel injection pumping apparatus

ABSTRACT

A fuel pumping apparatus includes a feed pump which supplies fuel to an injection pump through a control device. Associated with the injection pump is a device which is responsive firstly to the pressure intermediate the control device and the injection pump, and secondly to a pressure derived from the outlet of the feed pump and controlled by a valve which carries the pressure in accordance with the speed at which the apparatus is driven.

United States Patent Bakti LIQUID FUEL INJECTION PUMPING APPARATUS Aug.5, 1975 3,552,366 1/1971 Kemp .1 123/139 AQ Primary Ei\'mniner-Churles.l. Myhre Assistant E.\'uminerDaniel J. OConnor Attorney, Agent orFirm-Holman & Stern 1571 ABSTRACT A fuel pumping apparatus includes afeed pump which supplies fuel to an injection pump through a controldevice Associated with the injection pump is a device which isresponsive firstly to the pressure intermediate the control device andthe injection pump. and secondly to a pressure derived from the outletof the feed pump and controlled by a valve which carries the pressure inaccordance with the speed at which the apparatus is driven.

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PATENTED B 5 I975 SHEET LIQUID FUEL INJECTION PUMPING APPARATUS Thisinvention relates to liquid fuel injection pumping apparatus forsupplying fuel to internal combustion engines and has for its object toprovide such an apparatus in a simple and convenient form.

A liquid fuel injection pumping apparatus in accordance with theinvention comprises in combination, an injection pump including aplunger operable by a cam, the injection pump being driven in timedrelationship with the engine to which fuel is to be supplied, a feedpump for supplying fuel to the injection pump during the filling strokethereof, a fuel control device for controlling the quantity of fuelsupplied to the injection pump during the filling strokes thereof, thepressure of fuel intermediate the injection pump and the control deviceincreasing as the quantity of fuel supplied to the injection pump isincreased, a fluid pressure operable piston for controlling the timingof delivery of fuel to the engine, a servo valve for controlling theapplication ofliquid under pressure to one end of the piston, means forderiving a fluid pressure which varies in accordance with the speed ofthe engine, said fluid pressure being applied to the servo valve tocause movement thereof against the action of a spring thereby to allowliquid under pressure to act on the piston and fuel pressure operablemeans acting on said servo valve in addition to the action of thespring, said fuel pressure operable means being supplied with fuel underpressure from intermediate the injection pump and the control devicewhereby the position of the fluid pressure operable pis ton and therebythe timing of injection of fuel to the engine will vary in accordancewith the speed of the engine and also in accordance with the quantity offuel which is being supplied to the engine.

One example ofa liquid fuel injection pumping appa ratus in accordancewith the invention will now be described with reference to theaccompanying drawings in which:

FIG. 1 is a schematic layout of the apparatus,

FIG. 2 is a sectional side elevation of part of the apparatus shown inFIG. 1, and

FIGS. 3 and 4 show modifications of the portion of the apparatus shownin FIG. 2.

Referring to FIG. 1 of the drawings there is provided a feed pump whichsupplies fuel through a quantity control device 11 to a fuel injectionpump 12. The fuel injection pump is driven in timed relationship with anengine 13 and supplies fuel thereto during the injection strokesthereof. It will be appreciated that the injection pump may be of therotary distributor type. The quantity control device determines theamount of fuel supplied to the injection pump and hence the amount offuel supplied at each injection stroke. Such a device is well known andmay comprise a throttle valve such as is shown at 14 in thespecification of U.S. Pat. No. 3,552,366.

The injection pump is provided with a fluid pressure operable device 14which controls the timing of injection of fuel to the engine 13 and thisis supplied with three fluid pressures. The first of these pressures isderived from a point intermediate the control device 11 and theinjection pump 12. This pressure varies in accordance with the quantityof fuel which is supplied to the injection pump during the fillingperiods thereof and as the quantity of fuel supplied to the injectionpump increases so also does this pressure. The second pressure isderived from the outlet of the feed pump 10 by way of a control valve 15which modifies the feed pump pressure so that it varies in accordancewith the square of the speed at which the engine is driven. The thirdpressure supplied to the device 14 is obtained directly from the outletof the feed pump 10.

Referring now to FIG. 2 the device 14 is shown therein in greater detailas also is a portion of the injection pump. The latter includes aplunger 16 which through the intermediary of a roller 17 is movedinwardly by the action of cam lobes 18 which are formed on the internalperiphery of a cam ring 19 which is an gularly movable within a bodypart 20 of the apparatus.

The setting of the cam ring 19 determines the timing of injection offuel to the engine 13 and the angular set ting of the cam ring 19 isdetermined by the device 14. This includes a piston 21 which is slidablewithin a bore formed in the body part. Each end of the bore is closed bya cap 22 and the piston 21 is coupled to the cam ring 19 by means of atongue 23. Formed in the piston is a bore 24 the left hand end of whichis closed by a plug 25. Slidable within the bore 24 is a servo valve 26and the space intermediate the servo valve 26 and the plug 25 issupplied with fuel at a pressure which varies in accordance with thesquare of the speed at which the engine is driven. The pressure isapplied to the servo valve by way of a passage 36 extending within thebody part and piston 21. In other words this is derived from the controlvalve 15.

Formed in the wall of the bore 24 is a port 27 which communicates withthe left hand end of the piston by way of a passage formed therein. Theport 27 in an equilibrium position, is covered by a land of the servovalve. The left hand side of the land forms an end wall of a groovewhich is formed in the servo valve and this groove is in constantcommunication with the outlet of the feed pump 10 by way of a passage 37in the body part and piston 21. In other words the land is subjected tothe third pressure referred to in FIG. 1. The right hand side of theland is exposed to a low pressure such as that which exists within thebody part of the apparatus.

The plug 22 includes an extension 28 and within the plug and extensionis formed a recess 29 which is closed by a pipe connector 30. Within therecess 29 is located a spring 31 which acts on the flange of a push rod32 which extends through a bore in the extension into contact with theright hand end of the servo valve. Formed in the wall of the extensionis a restricted orifice 33 which communicates with the interior of thebody part of the apparatus and formed in the pipe union is a furtherrestricted orifice 34. The pipe union is connected to the pressure whichexists intermediate the control device 11 and the injection pump 12.

In operation and considering only the effect of the pressure which isdependent on the square of the speed, as this pressure increases theservo valve 26 will be moved towards the right against the action of thespring 31. [n so doing the land will uncover the port 27 to the groovein the servo valve so that fuel from the outlet of the feed pump willflow to the left hand end of the piston and thereby cause movementthereof towards the right until the port 27 is again covered by theland. By this arrangement the movement of the servo valve is followedclosely by the equivalent movement of the piston 21 and this results inangular movement of the cam ring 19. If the pressure of fuel should fallthen the servo valve will move to the left to uncover the port 27 to thelow pressure which exists within the body part of the apparatus. Theservo valve may contact the plug 25 and the spring acting on the servovalve may move the piston towards the left, alternatively, the reactiondue to the rollers engaging the cam lobes may effect the movement of thepiston towards the left.

Considering now the effect of the pressure supplied through the pipeunion 30. The pressure within the re cess 29 which is dependent upon thepressure intermediate the control device 11 and the injection pump 12,acts on the end area of the push rod 32 and assists the action of thespring 31 as a result the position of the servo valve and therefore thepiston 2I, will depend both upon the speed at which the engine isoperating and also upon the pressure intermediate the control device IIand the injection pump which depends on the volume of fuel which issupplied to the injection pump during the filling stroke and thereforethe quantity of fuel which is being supplied to the engine during thedelivery strokes of the injection pump. The orifice 34 is provided toreduce the pressure which exists between the control device II and theinjection pump and the size of this orifice is carefully chosen inrelation to the effective area of the end of the push rod 32 so that theeffect of variation of the quantity of fuel supplied to the engine doesnot over-shadow the effect of variations of speed of the engine. Theorifice 33 is provided to ensure a continuous flow of fuel through therecess 29 and in addition it ensures that the variation in this pressureas will occur between the filling periods and delivery periods of theinjection pump is reduced to an acceptable level.

In the arrangement shown in FIG. 3 the pipe union 30 is omitted and theend cap 22 and the surrounding body part are modified to allow the fuelpressure which is dependent upon quantity, to be supplied to the recess29 it will be noted that in this case the orifice 34 is formed in theend cap 22.

In the arrangement shown in FIG. 4 a spring 35 is interposed between thepush rod 32 and the servo valve 26. This spring is a relatively lightspring and ensures that the servo valve 26 and therefore the piston 21are maintained in the fully retarded position for starting purposes. Assoon as the pressure which is dependent upon speed increasessufficiently the servo valve 26 moves into contact with the push rod 32and thereafter the spring 35 has no effect, the embodiment working inthe same manner as the embodiments shown in FIGS. 2 and 3.

I claim:

I. A liquid fuel injection pumping apparatus for supplying fuel tointernal combustion engines which apparatus comprises in combination: aninjection pump including a plunger operable by a cam, the injection pumpbeing driven in timed relationship with an engine to which fuel is to besupplied; feed pump means for supplying fuel to the injection pumpduring the filling stroke thereof; fuel control device means forcontrolling the quantity of fuel supplied to the injection pump duringthe filling strokes thereof, the pressure of fuel intermediate theinjection pump and the control device means increasing as the quantityof fuel supplied to the injection pump is increased; fluid pressureoperable piston means for adjusting the setting of said cam thereby tocontrol the timing of delivery of fuel to an engine; pressure responsiveservo valve means for controlling the application of liquid underpressure to one end of the piston means; fluid pressure means whichvaries in accordance with the speed of an engine; said fluid pressuremeans being applied to the servo valve means to cause movement thereofagainst the action of a spring thereby to allow liquid under pressure toact on the piston means, and fuel pressure operable means acting on saidservo valve means in addition to the action of the spring; passage meansthrough which said fuel pressure operable means is sujbected to fuelunder pressure from intermediate the injection pump and the controldevice means whereby the position of the fluid pressure operable pistonmeans and thereby the timing of injection of fuel to an engine will varyin accordance with the speed of that engine and also in accordance withthe quantity of fuel which is being supplied to that engine; said fuelpressure operable means comprising a push rod slidable in a plug servingto close one end of a cylinder containing the piston means, a springchamber defined in said plug, said spring being located in said chamber,one end of said push rod being located in said chamber and serving as anabutment for said spring, and the fuel under pressure intermediate theinjection pump and control device being supplied to said chamber,whereby the push rod transmits the spring force to the servo valve meansand also the force generated by the pressure intermediate the injectionpump and control device means acting on the push rod.

2. The apparatus as claimed in claim 1 including a further spring actingintermediate the push rod and the servo valve means, said furtherspring, in the absence of fuel or fluid pressure, acting to effectmovement of the piston means its maximum extend in the directionopposite to that in which it is moved by the fluid pressure.

3. The apparatus as claimed in claim 2, including a restricted passageleading from said chamber; said restricted passage opening to a drain;and a restrictor interposed in said passage means conveying fuelpressure to said spring chamber.

1. A liquid fuel injection pumping apparatus for supplying fuel tointernal combustion engines which apparatus comprises in combination: aninjection pump including a plunger operable by a cam, the injection pumpbeing driven in timed relationship with an engine to which fuel is to besupplied; feed pump means for supplying fuel to the injection pumpduring the filling stroke thereof; fuel control device means forcontrolling the quantity of fuel supplied to the injection pump duringthe filling strokes thereof, the pressure of fuel intermediate theinjection pump and the control device means increasing as the quantityof fuel supplied to the injection pump is increased; fluid pressureoperable piston means for adjusting the setting of said cam thereby tocontrol the timing of delivery of fuel to an engine; pressure responsiveservo valve means for controlling the application of liquid underpressure to one end of the piston means; fluid pressure means whichvaries in accordance with the speed of an engine; said fluid pressuremeans being applied to the servo valve means to cause movement thereofagainst the action of a spring thereby to allow liquid under pressure toact on the piston means, and fuel pressure operable means acting on saidservo valve means in addition to the action of the spring; passage meansthrough which said fuel pressure operable means is sujbected to fuelunder pressure from intermediate the injection pump and the controldevice means whereby the position of the fLuid pressure operable pistonmeans and thereby the timing of injection of fuel to an engine will varyin accordance with the speed of that engine and also in accordance withthe quantity of fuel which is being supplied to that engine; said fuelpressure operable means comprising a push rod slidable in a plug servingto close one end of a cylinder containing the piston means, a springchamber defined in said plug, said spring being located in said chamber,one end of said push rod being located in said chamber and serving as anabutment for said spring, and the fuel under pressure intermediate theinjection pump and control device being supplied to said chamber,whereby the push rod transmits the spring force to the servo valve meansand also the force generated by the pressure intermediate the injectionpump and control device means acting on the push rod.
 2. The apparatusas claimed in claim 1 including a further spring acting intermediate thepush rod and the servo valve means, said further spring, in the absenceof fuel or fluid pressure, acting to effect movement of the piston meansits maximum extend in the direction opposite to that in which it ismoved by the fluid pressure.
 3. The apparatus as claimed in claim 2,including a restricted passage leading from said chamber; saidrestricted passage opening to a drain; and a restrictor interposed insaid passage means conveying fuel pressure to said spring chamber.